Radiation-induced meningiomas: A case-control study at single center institution

Background: Our understanding of radiation induced meningiomas (RIM) is limited. It has been suggested that RIM harbor more aggressive cellular pathology and must be observed vigilantly. However, the actual recurrence rates of RIM compared to the sporadic meningiomas has yet to be defined.

Objective: We employ a single center case-control study to retrospectively assess recurrence rates between RIM (n = 12) and sporadic meningiomas (n = 118).

Methods: The criteria for the RIM group included the following: 1) History of intracranial clinical-dose radiation 2) Initial pathology other than meningioma, 3) Radiation administered greater than 5 years prior to meningioma onset. Recurrence rates, extent of resection and outcomes were analyzed.

Results: There was a significant difference in recurrence rates between the RIM group and sporadic meningioma: 50% vs. 5% respectively, p = 0.004. There was no significant difference in race, preoperative tumor volume, extent of resection, Ki67, or age between the two groups. Multivariate analysis demonstrated that size (OR 0.95 95%CI (0.92-0.99)), extent of resection (OR 1.08 95%CI (1.01-1.14)), WHO grade (OR 160.24 95% CI (6.32-74509)) and history of previous radiation (OR 1.28 95%CI (1.01-1.62)) were independent risk factors for recurrence. RIM patients had significantly higher proportion of atypical or malignant histology compared to sporadic patients (p < 0.0001).

Conclusion: RIM patients may have a higher predisposition for tumor recurrence than patients with sporadic RIM. The use of Ki67 indices may help identify patients with a higher risk of tumor recurrence. Prospective studies focusing on newly diagnosed patients with RIM may help identify an optimal surveillance and treatment plan.